Apparatus for baking fluorescent lamp tubing and the like



Dec. 30, 1941. R.M. GARDNER 2,267,727

APPARATUS FOR BAKING FLUORESCENT LAMP TUBING AND THE LIKE I Filed Jan. 27, 1940 3 Sheets-Sheet l -ll II II N "A 1 I Rom/v0 M. GARDNER,

' INVENTOR.

Dec. 30, 1941.

R. M. GARDNER 2,267,727

APPARATUS FOR B AKING FLUORESCENT LAMP TUBING AND THE LIKE Filed Jan. 27, 1940 RO AND GARDME INVENTOR.

3 Sheets-sleet 2 .Dec. 30, 1941;

R. M. GARDNER 2,267,727

APPARATUS FOR BAKING FLUORESCENT LAMP TUBING AND THE LIKE Filed Jan 27, 1940 3 Sheets- Sheet :5

OLA/v0 M. GARpNER,

- INVENT OR.

I BY M ATTORNEY.

Patented Dec. 30, 1941 APPARATUS roa BAKING FLUORESCENT LAMP TUBING AND rm: LIKE Roland M. Gardner, Swampscott, Mass., assignor to Hygrade Sylvania Corporation, a corporation of Massachusetts Application January 27, 1940, Serial No. 316,022

8 Claims. (01. 263-6) The present invention relates particularly to machines and processes for the manufacture of intemally-coated tubing, such as luminescentcoated glass tubing, but many features of the invention are suitable for use in the allied arts.

Luminescent-coated tubing is usually prepared by apply g, to the interior of a tube of glass or the like, a suspensionof luminescent material in a vehicle containing some viscous substance such as nitrocellulose, baking the tube until the binder decomposes to a dark residue of carbon or the like, and continuing the baking, in the presence of some oxygen, to remove the residue, leaving a coating of the luminescent material.

An object of the present invention is to provide a machine which will automatically bake such tubing uniformly in a manner suitable for factory production of the tubing for use in lamps.

A feature of the invention is an oven employing down-draft burners; and another feature is the arrangement of a considerable number of such burners in staggered relationship. A further feature is a series of rollers to carry the coated tube through the oven; and a pushing device for propelling the tube from roller to roller. Yet another is the arrangement of said rollers to permit expansion; and still antiher is an air draft through the baking tubes to facilitate removal of the carbon. Still another is an arrangement of channel iron and steel sheet to form the walls of such an oven.

Other objects, features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. l is a longitudinal view, partly in section of a device according to the invention;

Fig. 2 is a top view of the same device;

Fig. 3 is a profile view of the pushing device of Fig. 1;

Fig. 4 is an enlarged longitudinal section of the device of Fig. 1, taken on the side opposite Fig. l, and with a ventilation system added; and- Flg- 5 is a section transverseto that of Fig. 4, showing the interior of one of the rollers.

In Fig. 1, the tubes to be baked are placed into the end I, of the machine. are baked and emerge at the end 2. of the. machine, onto themclined table 3.

Inside the machine the coated tubes. such as tube 4, shown in the sectional part of Fig. 1, rest between the rollers 5, which are spaced apartbut are close enough together to prevent the tube 4, from falling through the space between them. The rollers 5, are kept in rotation by the motor 5, which turns the sprockets ,I, by means of the continuous chain 8. One sprocket is attached to each roller. The

tube 4, is pushed from roller to roller by the pushing fork 9; the tube progressing through the machine from end I, to end 2, with the rollers 5,

rotating in the direction shown by the arrow, so that the top of the roller is moving in a direction opposite to the direction in which the tube [progresses through the machine. The rotation of the tubes 4, insures uniform heating around their circumferences.

A fork 9, is set along the rollers 5, in the space between rollers. The fork 9, is attached to the arm Ill, which in turn is attached to the longer arm I I, which is itself attached to a short arm I2, bearing the follower I3, actuated by cam I4; the arm I2 being pivoted on a bearing I5. The cam I4 is kept rotating; it may be operated if desired from the motor 6, through a reduction gear if necessary, so that the tube 4 may revolve several times in each position before being pushed into the next position. For clarity,

only one fork 9, is shown; actually one is used between each two rollers.

The oven IE encloses the space above the roller 5, in which the tube 4 progresses through the machine.

ers 22, which are ceramic cups, are shown at the ends of the supply lines H, which are fed by the gas and air lines, 23 and 24, respectively. The burners, shown in more detail in Fig. 4, are, of course used to heat the oven I6. They are placed in a staggered formation, as shown by the section in the middle of Fig. 2, in order to insure uniform heating of the tubes 4, as they pass under them. The burners are arranged so that no two of them center on the same longitudinal line. This insures, that as a, tube 4, passes through the oven, there will be no excessive heating of any one portion of the tube. The burners The oven II; is heated by burners, shown in Figs. .2 and 4, attached to the supply prevent their rolling off. Th leg Lu, may sunscores? on face 25, of the angle ore staggered with reis connected to the exhaust system. These sir soect to those on face This permits the inlets ore necesssryonly at time middle of time beveled edge 2?, of the angle, which edge is oven, and are n used over the rollers at the one which pushes against the tube i being col ci o and which thus comes in closest cont the heat, to expend considerab o inc the trueness of the "u ports the iron chomrel They t- .rougn they ere the dow v e3 3 one oven, on which may have the stop me csses ice helpful o n :forlz. Bearing; sun-= port the lower end oi "he 1') ole.

The burners 22, cent :ise the ceramic cups SE), vcnome twisting o" t M which are the terminals of the use mmture by s; plate l A cried over e cut-out nor: supply lines ll, which pass througnthe roof or tion or the angle-iron the oven. When the device is in operation, the shafts so,

The exhaust looses 35, at either end of the oven in the middle of the furnace may extend out of ere connected to an exhaust system 36 to remove the trance 28 on inch more then do those at the fumes and the like from the oven. The exhaust ends of the iurnoce, so great is the expansion. should be capable of regulation. Toe annular ring so at one end of the steel roller Fig. 5 shows a detail vertical cross-section 5 is fixed to the steel tubing as by pin 53, but the through the machine, taken through one of the annular rings on and 5?, inside the tubing, are

' rollers 5. The oven side-Wells 3E5, which form the not lined to the letter, but allow it to slide slong support for the oven roof 32?, are shown composed under its expansion. Pin 53 merely fixes the ring of the iron channel 3?, covered on the oven-into the shaft. The ennulsr ring should be stagterior side by the stainless steel sheet The so sored in position from rod to rod so that. they oven ,roof is seen to comprise the iron channel will not all line up to produce uneven heating benms 36. By comparison with Fig. 4, these iron of the tube due to their efiect.

channels will be seen to be placed with their lnthe some Fig.5,the pushing fork ii, isshown open end facing downward into the oven, and with the staggered slots 29, described in connecwith that open end covered by a. reversed channel so tion with Fig. 3. The sprocket 7] is shown, as is piece 39, of thin stainless steel. The stainless the chain 8. operating the sprocket. The addisteel acts as s. reflector to keep the host in the tionel idler sprocket 58, may be used to keep the oven, and the dead air space between. the iron chsin tout at its top and the chain may be left channel 3i, and the stainless steel piece 3%, acts sioclr at the bottom of the sprocket, as indicated. as heat insulation. The same efiect is also obso The steel cover pistes and may be used over mined, of course, in the side Well to, which is the open end oi the channels 15,, if desired.

similarly arranged. Over the iron channel For convenience, the burners 222 are not shown pieces in the roof, however, is placed a layer of other insulation such as the magnesium bricks In opere ion, the coated tube 5, to be baked is burners are made small, or replaced Toy loose Tne rollers 5, rotate the tube t, insuring an even insulating material, to facilitate changing of the heating sround diameter, and every few sec burners 22 when necessary for repairs. onols, the pushers 9, rise to push tire-tube over The ducts (ill, run along the outside oi the oven, onto the next roller. The rollers themselves to discharge a current of sir through the openso should rotote the tube in the direction it would ing i569, onto the bearings 5i and cooling them. rotete it rolled through the oven from the some These sir ducts are connected to the air supply end. As the tube progresses through the oven system iii. A current of air is admitted at the posses under the loumers which are stag side of the oven through the open end ii oi the gored so that the portion of e directly under supply line 62, at a height such that the air TD ourner changes progressively es the tube or s passes through the tubes being through the furnace. Similarly/gene snnulcr suns passing through the tube; to oxidize the carbon ports 39, inside the roller are staggered in which may be formed in the tube coating by the position from roller to roller, so that any "n t; r baking process, the air current is exhausted cit cold spot produced in the tubel, by variation the other side of the oven by the duct '33, which in support inside the roller will also move pro- 83, so. The bricks or; in the neighborhood of the pieced on the rollers 5, end i, n the machine.

enema? gressively along the tube 4, as the tube goes through the oven. In that-way, an extremely uniform baking is obtained, with a consequent preservation of the original uniformity of the' coated tube.

As the tube 4, progresses through the furnace, the coating inside the tube gradually assumes a dark, brownish or black color, due to decomposidown the inclined plane 3, and kept from rolling off by the stop 28.

If the machine is built to bake tubing of the size used in standard fluorescent lamps, say tubing of 1% diameter, then tubing of the types used in the luminous sign industry, of say 15 mm. diameter, will fall through the space between rollers. However, I find that if several pieces of such smaller tubing are placed inside a seamless steel tube of the larger diameter, say 1%", the steel tube with the glasstubes inside, can be itself run through the furnace, and the smaller tubes inside it will be processed satisfactorily. If such a method is used, the steel tubing used as a container is preferably foraminous or perforated with a number of holes. The tubing baked in that manner will generally be found much straighter after processing than .before, due to tween successive rollers; means for raising the forks; and a series of burners between the top of the oven and the rollers to direct heat downwardly toward the rollers.

3 2.-'The machine of claim 1, mechanism for rotating the rollers, and mechanism actuated by said first-mentioned mechanism, for raising the series of forks at recurrent intervals equal to the time of several revolutions of the rollers.

3. The machine of claim 1, and: mechanism for rotating the rollers; mechanism actuated by said first-mentioned mechanism, for raising the series of forks at recurrent intervals equal to the time of several revolutions of the rollers; and an air inlet at the middle of the oven, said inlet being set to direct air into one end of the tube being baked.

4. The machine of claim 1 and: mechanism for rotating the rollers; mechanism actuated by said first-mentioned mechanism, for raising the series of forks at recurrent intervals equal to the time of-several revolutions of the rollers; and an air inlet at the middle of the oven, said inlet being set to direct air into one end of the tube being baked; and in which the forks are slotted angle- 'steel pieces.

5. The machine of claim 1 and: mechanism for rotating the rollers; mechanism actuated by. said first-mentioned mechanism, for raising the series of forks at recurrent intervals equal to the time of several revolutions of the rollers; and an air inlet at the middle of the oven, said inlet being set to direct air into one end of the tube being baked; which the oven comprises a frame of channel irons placed with the open ends of the channels facing the interior of the oven, and stainless sheet-steel channels covering theopen ends of the channels, and 'in which the forks comprise slotted angle-steel pieces,

6. The machine f claim 1, and an air inlet at the middle of the oven, said inlet being set to direct air into, one end of the tube being baked.

'7. Themachine of claim 1, in which the refractory forks are slotted angle-steel pieces.

.8. The machine of claim 1,,in which the oven comprises a frame of channel irons placed with the open ends of the channels facing the interior of said oven and stainless steel channels covering the open ends of the iron channels. ROLAND M. GARDNER. 

